Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds a genuinely useful operational fact not in any structured field: a fixed cost of 5 points per successful run, which is important for an agent budgeting calls. It omits auth/rate-limit context, but against rich annotations this is solid.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tightly packed sentences: the capability and its output fields first, the cost second. Every clause earns its place and nothing is redundant.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

There is no output schema, yet the description lists the returned fields, and annotations cover the safety profile while the description covers cost. For a single-parameter lookup this is close to complete, missing only explicit sibling routing and any error/not-found behavior.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the 'item' parameter is fully documented in the schema, including the fact it accepts an ID or URL and an example value. The description restates 'by item ID' but adds no format or edge-case detail beyond the schema, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description gives a specific verb ('Get'), resource ('eBay listing details'), and an identifier input ('by item ID'), then enumerates the returned fields (title, price, condition, images, seller). It clearly reads as a single-item lookup, but it never names a sibling (e.g. run_ebay_item_search) to disambiguate the retrieval-vs-search boundary.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Using 'by item ID' implies this is for fetching one known listing rather than searching, which contrasts with run_ebay_item_search. However, there is no explicit when-to-use/when-not statement, no prerequisite about obtaining an item ID, and no named alternative, so the guidance is only implied.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.